Multi-Method Geophysical Investigation of Fault Structures in the Northern Upper Rhine Graben: Insights from the NeoNORG Project

Within the framework of the project Neotectonics in the Northern Upper Rhine Graben (NeoNORG), we used a multi-method geophysical approach to obtain a detailed understanding of the fault structures within the sedimentary basin.

Using parts of a 3D seismic data set originally conducted by the petroleum industry we were able to obtain a detailed 3D structural model. It consists of two main faults originating from the basement at a depth of 2 km to about 350 m below the surface. To close the gap between the 3D Seismic data and the surface, we conducted 2D P-wave profiles with geophone spacings of 2.5 m. For the uppermost 200 m, an even higher resolved image of the subsurface was obtained using 2D S-wave seismics with geophone spacings of 1 m. Geoelectrics with varying electrode spacings and georadar using 200Mhz antennas were used to resolve the uppermost 50 m.

The combination of these different geophysical investigation methods allowed us to trace the fault zones within the sedimentary basin from the crystalline basement at a depth of 2 km into the quaternary strata, several meters below the earth's surface. We thereby reveal the (neo)-tectonic activity of the investigated area. Overall, the study provides valuable insights into the development of fault zones in the Northern Upper Rhine Graben and demonstrates the importance of using a multi-method geophysical approach to investigate the tectonic development. The obtained fault outcrop at the surface is concurrently used to investigate the relationship of radon in soil gas and fault zones.